Design and characterization of a near-field gamma imager for in situ measurements of fuel rod deformations

A prototype of gamma imaging system has been developed for the detection of fuel rod deformations, based on the WidePIX hybrid pixel detector, associated with a collimator. The WidePIX detector used in the frame of these developments is made of 2 x 5 Timepix devices hybridized with a 1 mm-thick cadmium telluride semiconductor. A specific collimator was designed, offering the best compromise between mechanical feasibility, cost, signal-to-noise ratio and angular resolution, and making it possible to visualize the fuel rod deformations. In this work, we present the design of the collimator carried out by Monte-Carlo simulation, and experimental results obtained with this prototype on a Cs-137 and Co-60 metrological irradiator.